PROJECT SUMMARY/ABSTRACT The ultimate goal of this Mentored Patient-Oriented Research Career Development Award (K23) is to develop the applicant into an independent investigator prepared to lead ethical, large-scale, and rigorously designed health services research focused on high-risk emerging adults (EAs; aged 18-25). Specifically, the applicant will focus on improving access to and engagement in evidence-based practices (EBPs) for EAs with opioid and other substance use (SU) and co-occurring justice system (JS) involvement, via use of paraprofessional coaches. The proposed career development and research plan builds on the applicant's prior training in clinical and developmental psychology, EBPs, and SU. Through the proposed training plan, the applicant will: (1) gain direct experience conducting ethical health services research with vulnerable populations; (2) attain knowledge and skills for measurement, methodologies, and the interplay of key developmental outcomes in EAs with opioid and other SU problems; (3) advance expertise in the complex statistical methods required for health services research, including mixed methods research, and (4) facilitate professional development as an independent health services researcher focused on EAs with opioid and other SU problems via extensive training in grant writing, grants management, and development of a health services program of research. Training activities will include formal training and mentorship from a team of experts in the fields of SU, randomized clinical trials, EA peer support, bioethics, justice, implementation, and advanced health services statistical methods; intensive training in conducting ethical research with high-risk populations; coursework and lectures on implementation science, qualitative research methods, statistics, and protection of human subjects; and participation in scientific workshops and conferences. The applicant will apply these skills to pilot research aimed at using paraprofessional coaches to increase engagement and access to EBPs (i.e., contingency management for SU and vocational/educational coaching) for EAs with SU and JS involvement. In partnership with parole and probation, EAs with SU will be randomized to work with paraprofessional coaches either with or without lived experience (i.e., successful SU recovery). Although using peer paraprofessional coaches (those with lived experience) is becoming more popular and supported at the federal level, the outcome of this work on the paraprofessional coaches themselves, especially for EAs, is largely unexplored. The proposed study will use both quantitative and qualitative methods to gain a better understanding of the impacts on both the coaches and their EA clients using the Consolidated Framework for Implementation Research (CFIR). Given the high rates and particularly detrimental effects of SU for EAs with JS involvement, the goals of this project have the potential to address an important and costly public health problem. As SU and poor vocational/educational attainment greatly increases the likelihood of recidivism, innovative strategies to reduce opioid and other SU for EAs is critical, along with understanding the effects on the service providers (i.e., paraprofessional coaches).